In general, a white light emitting diode (LED) recently prominent due to the use in lighting devices, LCD backlights, automobile lighting devices, and the like, includes an LED emitting blue or near ultraviolet light and as an excitation source, a phosphor converting a wavelength of the light emitted from the LED into visible light.
A representative method of implementing the white LED includes employing a blue light emitting diode formed of an InGaN-based material having a wavelength of 450 to 550 nm as a light emitting element and employing a YAG-based phosphor emitting yellow light and represented by a compositional Formula of (Y,Gd)3(Al,Ga)5O12 as a phosphor. In the white LED, blue light emitted from the light emitting element is incident onto a phosphor layer and repeatedly absorbed and scattered within the phosphor layer. Yellow light formed by wavelength converted blue light and a portion of the incident blue light are mixed, such that the blue light absorbed in the phosphor through the repeated process may appear to human eyes as white light. However, oxide-based phosphors such as silicate or the like generally tend to be degraded in luminous intensity when a wavelength of an excitation source is above 400 nm, and accordingly are not appropriate for implementing white light having high brightness using blue light. Garnet based phosphors which is represented by YAG have excellent excitation efficiency and luminous efficiency in blue light but tend to be degraded in luminous efficiency at high temperature.
In recent years, nitride based phosphors, so-called LSN phosphors having a compositional Formula of La3Si6N11 have been reported and appreciated as having superior high temperature characteristics and reliability. However, LSN phosphors may provide yellow phosphors having a broad emission bandwidth and high luminous efficiency, but have low luminous efficiency in a wavelength band of about 550 nm or more.